Without having all the configs and info, I'll take a shot at this.
Since this is only happening at some sites you may want to look at utilization on the
frame links. If your utilization is so high that you are missing eigrp hellos, the
routing protocol may decide that the route is not there and the router will use the
next
best route in the routing table which would be the floating static that you have
configured for DDR backup.
If the above is not the case, then perhaps you have a combination of two problems:
First, you do not have correct bandwidth statements on the interfaces and second you
are
not being specific enough when you define interesting traffic to bring up the backup
link. What you want to do is write an access list that will deny eigrp but permit
everything else. This will be used in the dialer list then applied to the BRI
interface
with the 'dialer-group' command. This only causes eigrp to NOT bring up the link but
will permit eigrp traffic once the link is up.
Another thing to be careful of is that if the frame link is up and the isdn line does
become active, you don't want that remote site to become a transit path to the rest of
the network. You should use distribute-lists at the remote sites to only advertise
networks behind the remote routers.
Anyway, just my humble opinion without all the info. Hope it helps. If not and you
are
able to provide additional information, I would be glad to try to help more.
-dennis
Jim Bond wrote:
> Hello,
>
> We have 4000 router and 5200 router at central office,
> 2500 routers and 3640 routers at branch office. 4000
> and 2500s are connected with frame relay, 5200 and
> 3640s are connected with ISDN backup. Eigrp is the
> only protocol. We have a default route from 4000 and
> it got advertised on 2500s and 3640s as AD /170. We
> also configure a default route on 3640s with AD /200
> so in case frame is down, /200 default route will take
> over and then can bring up ISDN.
>
> The problem is sometimes when frame is ok, 3640 router
> default route changes to AD /200 and hence brings up
> ISDN backup (3640 also serves as RAS server). When I
> do "clear ip route", the AD /170 default route will
> come back again, then some days later, it'll get
> replaced by the AD /200 one.
>
> We use the same IOS on all routers but this only
> happened on some branch offices, not all of them. Any
> idea what wrong it is?
>
> Thanks in advance.
>
> Jim
>
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